Sequence allocating method, transmitting method and wireless mobile station device

ABSTRACT

It is an object to provide a sequence allocating method that, while maintaining the number of Zadoff-Chu sequences to compose a sequence group, is configured to make it possible to reduce correlations between different sequential groups. This method comprises the steps of setting a standard sequence with a standard sequence length (Nb) and a standard sequence number (rb) in a step (ST 101 ), setting a threshold value (Xth(m)) in accordance with an RB number (m) in a step (ST 103 ), setting a sequence length (N) corresponding to RB number (m) in a step (ST 104 ), judging whether |r/N−rb/Nb|=Xth(m) is satisfied in a step (ST 106 ), including a plurality of Zadoff-Chu sequences with a sequence number (r) and a sequence length (N) in a sequence group (rb) in a step (ST 107 ) if the judgment is positive, and allocating the sequence group (rb) to the same cell in a step (ST 112 ).

TECHNICAL FIELD

The present invention relates to a sequence allocating method,transmitting method and radio mobile station apparatus that are used ina cellular radio communication system.

BACKGROUND ART

In 3GPP LTE (3rd Generation Partnership Project Long Term Evolution), aZadoff-Chu sequence (“ZC sequence”) is adopted as a reference signal(“RS”) that is used in uplink. The reason for adopting a ZC sequence asan RS is that a ZC sequence has a uniform frequency characteristic andhas good auto-correlation and cross-correlation characteristics. A ZCsequence is a kind of CAZAC (Constant Amplitude and ZeroAuto-correlation Code) sequence and represented by following equation 1or equation 2.

$\begin{matrix}\left( {{Equation}\mspace{14mu} 1} \right) & \; \\{{a_{r}(k)} = \left\{ \begin{matrix}{{\mathbb{e}}^{{- j}\frac{2\pi\; r}{N}{({{k^{2}/2} + {qk}})}},} & {N\text{:}\mspace{14mu}{even}} \\{{\mathbb{e}}^{{- j}\frac{2\pi\; r}{N}{({{{k{({k + 1})}}/2} + {qk}})}},} & {N\text{:}\mspace{14mu}{odd}}\end{matrix} \right.} & \lbrack 1\rbrack \\\left( {{Equation}\mspace{14mu} 2} \right) & \; \\{{a_{r}(k)} = \left\{ \begin{matrix}{{\mathbb{e}}^{j\frac{2\pi\; r}{N}{({{k^{2}/2} + {qk}})}},} & {N\text{:}\mspace{14mu}{even}} \\{{\mathbb{e}}^{j\frac{2\pi\; r}{N}{({{{k{({k + 1})}}/2} + {qk}})}},} & {N\text{:}\mspace{14mu}{odd}}\end{matrix} \right.} & \;\end{matrix}$

In equation 1 and equation 2, “N” is the sequence length, “r” is the ZCsequence number, and “N” and “r” are coprime. Also, “q” is an arbitraryinteger. It is possible to generate N−1 quasi-orthogonal sequences ofgood cross-correlation characteristics from a ZC sequence having thesequence length N of a prime number. In this case, the cross-correlationis constant at √N between the N−1 quasi-orthogonal sequences generated.

Here, in the RS's that are used in uplink, the reference signal forchannel estimation used to demodulate data (i.e. DM-RS (DemodulationReference Signal)) is transmitted in the same band as the datatransmission bandwidth. That is, when the data transmission bandwidth isnarrow, a DM-RS is also transmitted in a narrow band. For example, ifthe data transmission bandwidth is one RB (Resource Block), the DM-RStransmission bandwidth is also one RB. Likewise, if the datatransmission bandwidth is two RB's, the DM-RS transmission bandwidth isalso two RB's. Also, in 3GPP LTE, one RB is comprised of twelvesubcarriers. Consequently, a ZC sequence having a sequence length N of11 or 13 is used as a DM-RS that is transmitted in one RB, and a ZCsequence having a sequence length N of 23 or 29 is used as a DM-RS thatis transmitted in two RB's. Here, when a ZC sequence having a sequencelength N of 11 or 23 is used, a DM-RS of 12 subcarriers or 24subcarriers is generated by cyclically expanding the sequence, that is,by copying the head data of the sequence to the tail end of thesequence. On the other hand, when a ZC sequence having a sequence lengthN of 13 or 29 is used, a DM-RS of 12 subcarriers or 24 subcarriers isgenerated by performing truncation, that is, by deleting part of thesequence.

As a method of allocating ZC sequences, to reduce the interferencebetween DM-RS's that are used between different cells, that is, toreduce the inter-cell interference of DM-RS, in each RB, ZC sequences ofdifferent sequence numbers are allocated to adjacent cells as DM-RS's.The data transmission bandwidth is determined by the scheduling in eachcell, and therefore DM-RS's of different transmission bandwidths aremultiplexed between cells. However, if ZC sequences of differenttransmission bandwidths, that is, ZC sequences of different sequencelengths, are multiplexed, a specific combination of ZC sequence numbershas a high cross-correlation.

FIG. 1 is a diagram illustrating cross-correlation characteristicsbetween ZC sequences in combinations of different sequence numbers,which are acquired by computer simulation. To be more specific, FIG. 1illustrates the cross-correlation characteristics between a ZC sequenceof a sequence length N=11 and sequence number r=3, and ZC sequences of asequence length N=23 and sequence numbers r=1 to 6. In FIG. 1, thehorizontal axis represents the delay time using the number of symbols,and the vertical axis represents the normalized cross-correlationvalues, that is, the values dividing the cross-correlation values by N.As shown in FIG. 1, the maximum cross-correlation value is very highwith the combination of a ZC sequence of r=3 and N=11 and a ZC sequenceof r=6 and N=23, and is about three times higher than thecross-correlation value in the single transmission bandwidth, 1/√N, thatis, 1/√11.

FIG. 2 is a diagram illustrating the inter-cell interference of DM-RS ina case where specific combinations of ZC sequences that increasecross-correlation are allocated to adjacent cells. To be more specific,a ZC sequence of r=a and N=11 and a ZC sequence of r=b and N=23 areallocated to cell #A, and a ZC sequence of r−e and N=23 and a ZCsequence of r=d and N=11 are allocated to cell #B. In this case, thecombination of the ZC sequence of r=a and N=11 allocated to cell #A andthe ZC sequence of r=c and N=23 allocated to cell #B, or the combinationof the ZC sequence of r=b and N=23 allocated to cell #A and the ZCsequence of r=d and N=11 allocated to cell #B, increases the inter-cellinterference of DM-RS, and, consequently, degrades the accuracy ofchannel estimation and degrades the data demodulation performancedegrades significantly.

To avoid such problems, the ZC sequence allocating method disclosed inNon-Patent Document 1 is used in a cellular radio communication system.To reduce inter-cell interference, Non-Patent Document 1 suggestsallocating a combination of ZC sequences of high cross-correlation anddifferent sequence lengths, to a single cell.

FIG. 3 is a diagram illustrating the ZC sequence allocating methodsdisclosed in Non-Patent Document 1 and Non-Patent Document 2. In FIG. 3,the example shown in FIG. 2 is used. As shown in FIG. 3, a combinationof ZC sequences of high cross-correlation, that is, a combination of aZC sequence of r=a and N=11 and a ZC sequence of r=c and N=23, isallocated to a single cell (cell #A in this case). Also, anothercombination of ZC sequences of high cross-correlation, that is, acombination of a ZC sequence of r=d and N=11 and a ZC sequence of r=band N=23, is allocated to a single cell (cell #B in this case). In thesingle cell, transmission bands are scheduled by one radio base stationapparatus, and, consequently, ZC sequences of high correlation allocatedto the same cell, are not multiplexed. Therefore, inter-cellinterference is reduced.

Also, Non-Patent Document 2 proposes a method of finding a combinationof ZC sequence numbers, which are used in RB's (hereinafter referred toas a “sequence group”). ZC sequences have a feature of having highercross-correlation when the difference of r/N, that is, the difference ofsequence number/sequence length is smaller. Therefore, based on asequence of an arbitrary RB (e.g. one RB), ZC sequences that make thedifference of r/N equal to or less than a predetermined threshold, arefound from the ZC sequences of each RB, and the multiple ZC sequencesfound are allocated to a cell as one sequence group.

FIG. 4 is a diagram illustrating a sequence group generation methoddisclosed in Non-Patent Document 2. In FIG. 4, the horizontal axisrepresents r/N, and the vertical axis represents the ZC sequence of eachRB. First, the reference sequence length Nb and reference sequencenumber rb are set. Hereinafter, a ZC sequence having the referencesequence length Nb and reference sequence number rb is referred to as a“reference sequence.” For example, if Nb is 13 (which is the sequencelength associated with one RB) and rb is 1 (which is selected between 1and Nb−1), rb/Nb is 1/13. Next, ZC sequences that make the difference ofr/N from the reference rb/Nb equal to or less than a predeterminedthreshold, are found from the ZC sequences of each RB to generate asequence group. Also, the reference sequence number is changed, and, inthe same process as above, other sequence groups are generated. Thus, itis possible to generate different sequence groups for the number ofreference sequence numbers, that is, it is possible to generate Nb−1different sequence groups. Here, if ranges for selecting ZC sequences,in which a difference from rb/Nb is equal to or less than apredetermined threshold, overlap between adjacent sequence groups, thesame ZC sequences are included in the plurality of sequence groups, andtherefore the sequence numbers overlap between cells. Therefore, toprevent ranges for selecting ZC sequences in adjacent sequence groupsfrom overlapping, the above predetermined threshold is set to, forexample, a value less than 1/(2Nb).

FIG. 5A and FIG. 5B illustrate examples of sequence groups generated bythe sequence group generation method disclosed in Non-Patent Document 2.Here, the sequence length. N is set to the prime number that is largerthan the maximum possible size of transmission in the transmissionbandwidth and that is the closest to this size, and, furthermore, thesequence length N is uniquely determined from the number of RB's. FIG.5A and FIG. 5B illustrate sequence groups (ZC sequence group 1 and ZCsequence group 2) comprised of ZC sequences that satisfy followingequation 3 in a case where the reference sequence length Nb is 13 andthe reference sequence number rb is 1 or 2. In equation 3, the thresholdXth is, for example, 1/(2Nb), (i.e. 1/26) to prevent the same sequencefrom being included in a plurality of sequence groups.|rb/Nb−r/N|≦Xth  (Equation 3)

Thus, according to the sequence allocating methods disclosed inNon-Patent Document 1 and Non-Patent Document 2, a sequence groupcomprised of ZC sequences that make a difference of r/N equal to or lessthan a predetermined threshold, that is, a sequence group comprised ofZC sequences having greater cross-correlation than a predeterminedthreshold, is generated, and the generated sequence group is allocatedto the single cell. By this means, it is possible to allocate acombination of ZC sequences of large cross-correlation and differentsequence lengths to the single cell, and reduce inter-cell interference.

-   Non-Patent Document 1: Huawei, R1-070367, “Sequence Allocating    method for E-UTRA Uplink Reference Signal”, 3GPP TSG RAN WG1 Meeting    #47bis, Sorrento, Italy 15-19 Jan. 2007-   Non-Patent Document 2: LG Electronics, R1-071542, “Binding method    for UL RS sequence with different lengths”, 3GPP TSG RAN WG1 Meeting    #48bis, St. Julians, Malta, Mar. 26-30, 2007

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, with the sequence allocating method disclosed in Non-PatentDocument 2, the threshold Xth related to a difference of r/N is a fixedvalue regardless of the number of RB's, and, consequently, the followingproblem arises.

FIG. 6 is a diagram illustrating a problem that arises when thethreshold Xth is set higher. As shown in FIG. 6, if the threshold Xth isset higher, ZC sequences located near the boundary of adjacent sequencegroups have a smaller difference of r/N, and therefore cross-correlationincreases. That is, the cross-correlation between sequence groupsincreases.

FIG. 7A and FIG. 7B illustrate problems that arise when the thresholdXth is set higher, using specific examples of sequence groups. In FIG.7A and FIG. 7B, the sequence group examples shown in FIG. 5A and FIG. 5Bare used. In the ZC sequences included in the two sequence groups (i.e.ZC sequence group 1 and ZC sequence group 2) shown in FIG. 7A and FIG.7B, the hatched ZC sequences have a smaller difference of r/N from andlarger cross-correlation with ZC sequences of other sequence groups.Here, as shown in FIG. 4, the number of ZC sequences in each RB is N−1at 1/N intervals in the range of r/N=0 to 1. Therefore, as shown in FIG.7A and FIG. 7B, when the number of RB's is larger, the number of ZCsequences increases that make a difference of r/N from a reference ZCsequence smaller than a threshold. Also, when the number of RB's islarger, that is, when the sequence length N is longer, the number ofhatched ZC sequences increases.

By contrast, when the threshold Xth is set smaller, the number of ZCsequences forming a sequence group decreases. Especially, when thenumber of RB's is smaller, that is, when the sequence length N isshorter, the number of sequences that are present in the range of r/N−0to 1 at 1/N intervals, N−1, decreases, and, consequently, when thethreshold is further smaller, the number of ZC sequences forming asequence group further decreases. Also, to randomize the influence ofinterference, if sequence hopping to switch sequence numbers atpredetermined time intervals is adapted and there are few candidates ofsequence numbers to be switched, the randomization of interferenceprovides no effect.

It is therefore an object of the present invention to provide a sequenceallocating method that can reduce cross-correlation between differentsequence groups while maintaining the number of ZC sequences forming asequence group that are allocated, in a cellular radio communicationsystem.

Means for Solving the Problem

The sequence allocating method of the present invention for Zadoff-Chusequences represented by equation 1 in a cellular radio communicationsystem, includes: a reference setting step of setting a referencesequence length Nb and a reference sequence number rb; a first thresholdsetting step of setting a first threshold based on the sequence lengthN; a selecting step of selecting a plurality of Zadoff-Chu sequences, inwhich a first difference representing a difference between rb/Nb and r/Nis equal to or less than the first threshold, from the Zadoff-Chusequences generated according to the equation 1; and an allocating stepof allocating the plurality of Zadoff-Chu sequences selected, to a samecell.

The radio mobile station of the present invention that transmitsZadoff-Chu sequences represented by equation 1 as a reference signal,employs a configuration having: a setting section that sets a thresholdbased on a sequence length N signaled from a radio base stationapparatus; a selecting section that selects a Zadoff-Chu sequence, inwhich a difference between rb/Nb and r/N is equal to or less than thethreshold, from the Zadoff-Chu sequences generated according to equation1, using a reference sequence number rb and a reference sequence lengthNb signaled from the radio base station apparatus; and a transmittingsection that transmits the selected Zadoff-Chu sequence as the referencesignal.

The transmitting method of the present invention whereby a radio mobilestation apparatus transmits Zadoff-Chu sequences represented by equation1 as a reference signal, in which the radio mobile station apparatusreceives a sequence length N and a reference sequence number rb signaledfrom the radio base station apparatus; selects a Zadoff-Chu sequence,which satisfies a condition that a difference between rb/Nb (where Nb isa reference sequence length) and r/N is equal to or less than athreshold associated with the sequence length N, using the receivedsequence length N and the received reference sequence number rb; andtransmits the selected Zadoff-Chu sequence as the reference signal.

Advantageous Effect of Invention

According to the present invention, it is possible to reducecross-correlation between different groups while maintaining the numberof ZC sequences forming sequence groups.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating cross-correlation characteristicsbetween ZC sequences in combinations of different sequence numbers,which are acquired by computer simulation, according to the prior art;

FIG. 2 is a diagram illustrating inter-cell interference between DM-RS'sin a case where specific combinations of ZC sequences that increasecross-correlation are allocated to adjacent cells, according to theprior art;

FIG. 3 is a diagram illustrating a method of allocating ZC sequencesaccording to the prior art;

FIG. 4 is a diagram illustrating a method of generating sequence groupsaccording to the prior art;

FIG. 5A is a diagram illustrating an example of a sequence groupgenerated by a sequence group generation method according to the priorart (ZC sequence group 1);

FIG. 5B is a diagram illustrating an example of a sequence groupgenerated by a sequence group generation method according to the priorart (ZC sequence group 2);

FIG. 6 is a diagram illustrating a problem with the prior art thatarises when the threshold Xth is set higher;

FIG. 7A is a diagram illustrating a problem with the prior art thatarises when the threshold Xth is set higher, using a detailed example ofa sequence group (ZC sequence group 1);

FIG. 7B is a diagram illustrating a problem with the prior art thatarises when the threshold Xth is set higher, using a detailed example ofa sequence group (ZC sequence group 2);

FIG. 8 is a flowchart showing the process of a sequence allocatingmethod in a cellular radio communication system, according to Embodiment1 of the present invention;

FIG. 9 is a diagram illustrating a method of setting a threshold in asequence allocating method according to Embodiment 1 of the presentinvention;

FIG. 10A is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 1 ofthe present invention (ZC sequence group 1);

FIG. 10B is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 1 ofthe present invention (ZC sequence group 2);

FIG. 11 is a diagram illustrating a method of setting a thresholdaccording to a sequence allocating method according to Embodiment 1 ofthe present invention;

FIG. 12A is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 1 ofthe present invention (ZC sequence group 1);

FIG. 12B is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 1 ofthe present invention (ZC sequence group 2);

FIG. 13 is a block diagram showing the configuration of a radio basestation apparatus to which a sequence group is allocated, according toEmbodiment 1 of the present invention;

FIG. 14 is a block diagram showing the configuration inside a ZCsequence setting section according to Embodiment 1 of the presentinvention;

FIG. 15 is a block diagram showing the configuration of a radio mobilestation apparatus according to Embodiment 1 of the present invention;

FIG. 16 is a diagram illustrating the cross-correlation characteristicascertained by computer simulation according to Embodiment 2 of thepresent invention;

FIG. 17 is a flowchart showing the process of a sequence allocatingmethod in a cellular radio communication system according to Embodiment2 of the present invention;

FIG. 18 is a diagram illustrating a method of generating sequence groupsbased on the process of a sequence allocating method according toEmbodiment 2 of the present invention;

FIG. 19A is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 2 ofthe present invention (ZC sequence group 1);

FIG. 19B is a diagram illustrating an example of a sequence groupacquired by a sequence allocating method according to Embodiment 2 ofthe present invention (ZC sequence group 8);

FIG. 20A is a diagram illustrating an example of a sequence groupacquired when the number of RB's allowing sequences to be deleted, isset 10 or greater (ZC sequence group 1); and

FIG. 20B is a diagram illustrating an example of a sequence groupacquired when the number of RB's allowing sequences to be deleted, isset 10 or greater (ZC sequence group 8).

BEST MODE FOR CARRYING OUT INVENTION

Embodiments of the present invention will be explained below in detailwith reference to the accompanying drawings. Here, in these embodiments,components providing the same functions will be assigned the samereference numerals and overlapping explanations will be omitted.

Embodiment 1

FIG. 8 is a flowchart showing the process of a sequence allocatingmethod in a cellular radio communication system according to Embodiment1 of the present invention.

First, in step (hereinafter “ST”) 101, the reference sequence length Nband the reference sequence number rb are set for a generated sequencegroup. Here, the sequence number rb corresponds to the sequence groupnumber and is lower than Nb.

In ST 102, the number of RB's, m, is initialized to 1.

In ST 103, the threshold Xth(m) associated with the number of RB's m isset. Here, the method of setting the threshold Xth(m) will be describedlater.

In ST 104, the ZC sequence length N associated with the number of RB's mis set. The number of RB's “m” and the sequence length N are uniquelyassociated. For example, N is a prime number that is larger than themaximum possible size of transmission with the number of RB's, m, andthat is the closest to this size.

In ST 105, the sequence number r is initialized to 1.

In ST 106, whether or not r and N satisfy following equation 4 isdecided.|r/N−rb/Nb|≦Xth(m)  (Equation 4)

Following equation 5 is acquired from equation 4. Given that equation 4and equation 5 are equivalent, in ST 106, whether or not r and N satisfyequation 5 may be decided.(rb/Nb−Xth(m))×N≦r≦(rb/Nb+Xth(m))×N  (Equation 5)

In ST 106, if r and N are decided to satisfy equation 4 (“YES” in ST106), the process of ST 107 is performed.

In ST 107, a ZC sequence having a sequence number of r is determined asone of ZC sequences associated with the number of RB's m in the sequencegroup rb.

In ST 106, when r and N are decided not to satisfy equation 4 (“NO” inST 106), the process of ST 108 is performed.

In ST 108, whether or not r<N is decided.

In ST 108, if r<N is decided (“YES” in ST 108), the process of ST 109 isperformed.

In ST 109, the sequence number r is incremented by 1 like r=r+1, and theprocess moves to ST 106.

In ST 108, if r<N is not decided (“NO” in ST 108), the process of ST 110is performed.

In ST 110, whether or not m<M is decided. Here, M is the maximum valueof the number of RB's in the sequence group rb and corresponds to themaximum value of the transmission bandwidth.

in ST 110, if m<M is decided (“YES” in ST 110), the process of ST 111 isperformed.

In ST 111, the number of RB's m is incremented by one, like m=m+1, andthe process moves to ST 103.

In ST 110, if m<M is not decided (“NO” in ST 110), the process of ST 112is performed.

In ST 112, the generated sequence group rb is allocated to a singlecell, that is, a single radio base station apparatus.

Next, the method of setting the threshold Xth(m) will be explained usingtwo different cases. In above ST 103, it is possible to use either offollowing setting method 1 and setting method 2.

<Threshold Xth(m) Setting Method 1>

FIG. 9 is a diagram illustrating threshold Xth(m) setting method 1 in asequence allocating method according to the present embodiment. As shownin FIG. 9, the threshold Xth(m) is set smaller when an RB is greater.For example, as shown in following equation 6, the Xth(m) is set todecrease by a predetermined value every time the number of RB's mincreases.Xth(m)=1/(2Nb)−(m−1)×0.0012  (Equation 6)

By setting the threshold Xth(m) in this way, ZC sequences located nearthe boundary of adjacent sequence groups have a greater difference ofr/N, so that it is possible to suppress an increase ofcross-correlation. Also, by increasing the threshold Xth(m) associatedwith a smaller number of RB's, it is possible to increase the number ofZC sequences and maintain it above a predetermined number.

FIG. 10A and FIG. 10B illustrate examples of sequence groups acquired bythe sequence allocating methods shown in FIG. 8 and FIG. 9. To be morespecific, the sequence groups shown in FIG. 10A and FIG. 10B areacquired according to the following conditions and process. For example,to generate ZC sequence group 1 shown in FIG. 10A, in ST 101, Nb=13 andrb=1 are set. Here, Nb=13 represents the sequence length associated withthe number of RB's m=1, and the sequence number rb=1 corresponds to thesequence group number. Next, in the process of ST 102, the thresholdXth(m) associated with the number of RB's is set using above equation 6,and, in the process of ST 104 to ST 107, the sequence number r thatmakes the difference between rb/Nb and r/N equal to or less than thethreshold Xth(m) is selected, to generate ZC sequence group 1. Theconditions and process for generating ZC sequence group 2 shown in FIG.10B differ from those in the case of ZC sequence group 1, only insetting the reference sequence number rb to 2 in ST 101.

<Threshold Xth(m) Setting Method 2>

FIG. 11 is a diagram illustrating threshold Xth(m) setting method 2 in asequence allocating method according to the present embodiment. As shownin FIG. 11, a threshold for the number of RB's “m” is set, and thresholdXth(m) is set higher below the threshold for the number of RB's thanabove the threshold for the number of RB's. For example, as shown infollowing equation 7, the threshold for the number of RB's m is 10, and,if the number of RB's in is equal to or lower than 10, Xth(m) is set to½ Nb, and, if the number of RB's m is higher than 10, Xth(m) is set to ¼Nb. That is, the threshold Xth(m) is switched between two fixed valuesacross the sequence length N associated with the number of RB's of 10,and the fixed value associated with the sequence lengths N's associatedwith the numbers of RB's equal to or less than 10 is set lower than thefixed value associated with the sequence lengths N's associated with thenumbers of RB's greater than 10.Xth(m)=1/(2Nb)(in the case of 1≦m≦10)Xth(m)=1/(4Nb)(in the case of m≧11)  (Equation 7)

By setting the threshold Xth(m) in this way, ZC sequences located nearthe boundary of adjacent sequence groups have a grater difference ofr/N, so that it is possible to suppress an increase ofcross-correlation. Also, by increasing the threshold Xth(m) associatedwith the numbers of RB's lower than the threshold for the number of RB'sm, it is possible to increase the number of ZC sequences and maintain itabove a predetermined number.

FIG. 12A and FIG. 12B illustrate examples of sequence groups acquired bythe sequence allocating methods shown in FIG. 8 and FIG. 11. To be morespecific, the conditions and process for acquiring the sequence groupsshown in FIG. 12A and FIG. 12B (i.e. ZC sequence group 1 and ZC sequencegroup 2) differ from the conditions and process for acquiring thesequence groups shown in FIG. 10A and FIG. 10B (i.e. ZC sequence group 1and ZC sequence group 2), only in using equation 7, instead of equation6, for the method of setting the threshold Xth(m).

Next, the operations of a radio base station apparatus that is presentin a cell, to which sequence groups generated based on the sequenceallocating method according to the present embodiment are allocated,will be explained.

FIG. 13 is a block diagram showing the configuration of radio basestation apparatus 100, to which sequence groups are allocated, accordingto the present embodiment.

Encoding section 101 encodes transmission data and control signal for aradio mobile station apparatus that is present in the same cell as thatof radio base station apparatus 100, and outputs the encoded data tomodulating section 102. Here, the control signal includes the referencesequence length Nb and the reference sequence number rb associated withthe sequence group number, and the reference sequence length Nb and thereference sequence number rb are transmitted to, for example, radiomobile station apparatus 200, which will be described later, via abroadcast channel. The control signal also includes schedulinginformation showing the transmission bandwidth including, for example,the number of RB's for transmission allocated to radio mobile station200 and the sequence length N, and this scheduling information istransmitted to radio mobile station apparatus 200 via a control channel.

Modulating section 102 modulates the encoded data received as input fromencoding section 101 and outputs the modulated signal to RF (RadioFrequency) transmitting section 103.

RF transmitting section 103 performs transmission processing such as A/Dconversion, up-conversion and amplification on the modulated signalreceived as input from modulating section 102, and transmits the signalsubjected to transmission processing via antenna 104.

RF receiving section 105 performs reception processing such asdown-conversion and A/D conversion on a signal received via antenna 104,and outputs the signal subjected to reception processing todemultiplexing section 106.

Demultiplexing section 106 demultiplexes the signal received as inputfrom RF receiving section 105 into a reference signal, data signal andcontrol signal, outputs the reference signal to DFT (Discrete FourierTransform) section 107 and outputs the data signal and control signal toDFT section 114.

DFT section 107 transforms the time domain reference signal received asinput from demultiplexing section 106 into a frequency domain signal byperforming DFT processing, and outputs the transformed, frequency domainreference signal to demapping section 109 in channel estimating section108.

Channel estimating section 108 is provided with demapping section 109,dividing section 110, IFFT section 111, mask processing section 112 andDFT section 113, and estimates the channel based on the reference signalreceived as input from DFT section 107.

Demapping section 109 extracts, from the frequency band reference signalreceived as input from DFT section 107, a ZC sequence corresponding tothe transmission band of each radio mobile station apparatus 200, andoutputs the extracted ZC sequences to dividing section 110.

ZC sequence setting section 1000 calculates the ZC sequences used inradio mobile station apparatuses 200, based on the reference sequencelength Nb, the reference sequence number rb and the number of RB'sassigned to each radio mobile station apparatus 200, which are includedin control information received as input, and outputs the results todividing section 110. Here, the internal configuration and operations ofZC sequence setting section 1000 will be described later.

Dividing section 110 divides the ZC sequences corresponding to eachradio mobile station apparatus 200, calculated in ZC sequence settingsection 1000, by the ZC sequences actually used in each radio mobilestation apparatus 200 and received as input from demapping section 109,and outputs the division result to IFFT (Inverse Fast Fourier Transform)section 111.

IFFT section 111 performs IFFT processing on the division resultreceived as input from dividing section 110, and outputs the signalsubjected to IFFT processing to mask processing section 112.

Mask processing section 112 extracts the correlation value in the regionin which the correlation value of the desired cyclic shift sequence ispresent, that is, extracts the correlation value in the window part, byperforming mask processing on the signal received as input from IFFTsection 111, and outputs the extracted correlation value to DFT section113.

DFT section 113 performs DFT processing on the correlation valuereceived as input from mask processing section 112, and outputs thecorrelation value subjected to DFT processing to frequency domainequalization section 116. Here, the signal subjected to DFT processingoutputted from DFT section 113, represents the frequency response of thechannel.

DFT section 114 transforms the time domain data signal and controlsignal received as input from demultiplexing section 106, into thefrequency domain by performing DFT processing, and outputs thetransformed, frequency domain data signal and control signal todemapping section 115.

Demapping section 115 extracts the data signal and control signalcorresponding to the transmission band of each radio mobile stationapparatus 200, from signals received as input from DFT section 114, andoutputs the extracted signals to frequency domain equalization section116.

Frequency domain equalization section 116 performs equalizationprocessing on the data signal and control signal received as input fromdemapping section 115, using a signal which is received as input fromDFT section 113 in channel estimating section 108 and which representsthe frequency response of the channel, and outputs the signals subjectedto equalization processing to IFFT section 117.

IFFT section 117 performs IFFT processing on the data signal and controlsignal received as input from frequency domain equalization section 116,and outputs the signals subjected to IFFT processing to demodulatingsection 118.

Demodulating section 118 performs demodulation processing on the signalssubjected to IFFT processing received as input from IFFT section 117,and outputs the signals subjected to demodulation processing to decodingsection 119.

Decoding section 119 performs decoding processing on the signalssubjected to demodulation processing received as input from demodulatingsection 118, and extracts received data.

FIG. 14 is a block diagram showing the configuration inside ZC sequencesetting section 1000.

Threshold calculating section 1001 calculate the threshold Xth(m)according to above equation 6 or equation 7, using the number of RB's mincluded in control information received as input, and outputs theresult to sequence number calculating section 1002.

Sequence number calculating section 1002 calculates the sequence lengthN of a ZC sequence that can be used as a reference signal, based on thenumber of RB's m included in control information received as input, andoutputs the result to ZC sequence generating section 1004. Also,sequence number calculating section 1002 calculates the sequence numberr of a ZC sequence that can be used as a reference signal, based on thecalculated sequence length N, the reference sequence number rb and thereference sequence length Nb included in the control informationreceived as input, and the threshold Xth(m) received as input fromthreshold calculating section 1001, and outputs the result to parameterdetermining section 1003.

Parameter determining section 1003 selects one of usable r's received asinput from sequence number calculating section 1002, and outputs theresult to ZC sequence generating section 1004. To be more specific,parameter determining section 1003 selects r corresponding to theremainder acquired by dividing the frame number or slot number by thenumber of usable r's, that is, corresponding to the result of performinga modulo operation of the frame number or slot number by the number ofusable r's. For example, upon receiving as input four usable r's of r=a,b, e and d from sequence number calculating section 1002, parameterdetermining section 1003 selects r=a when a result of performing amodulo operation on the frame number or slot number by 4 is 0, selectsr=b when the result is 1, selects r=c when the result is 2, and selectsr=d when the result is 3. By this means, it is possible to realizesequence hopping.

ZC sequence generating section 1004 generates a ZC sequence according toequation 1 or equation 2, using “r” received as input from parameterdetermining section 1003 and “N” received as input from sequence numbercalculating section 1002, and outputs the result to dividing section110.

As described above, radio base station apparatus 100 signals thereference sequence number rb, the reference sequence length Nb and thenumber of RB's, to radio mobile station apparatus 200.

Next, radio mobile station apparatus 200 that generates a ZC sequenceused as a reference signal will be explained, using the referencesequence number rb, the reference sequence length Nb and the number ofRB's signaled from radio base station apparatus 100.

FIG. 15 is a block diagram showing the configuration of radio mobilestation apparatus 200 according to the present embodiment. Here, in FIG.15, the receiving system of radio mobile station apparatus 200 will beomitted, and the transmitting system alone will be shown.

In FIG. 15, similar to ZC sequence setting section 1000 provided inradio base station apparatus 100, ZC sequence setting section 1000provided in radio mobile station apparatus 200 calculates a ZC sequencebased on the reference sequence number rb, the reference sequence lengthNb and the number of RB's m included in control information transmittedfrom radio base station apparatus 100, and outputs the result to mappingsection 201.

Mapping section 201 maps the ZC sequence received as input from ZCsequence setting section 1000, to the transmission band of radio mobilestation apparatus 200, and outputs the mapped ZC sequence to IFFTsection 202.

IFFT section 202 performs IFFT processing on the ZC sequence received asinput from mapping section 201, and outputs the ZC sequence subjected toIFFT processing to RF transmitting section 203.

RF transmitting section 203 performs transmission processing such as D/Aconversion, up-conversion and amplification on the ZC sequence receivedas input from IFFT section 202, and transmits the signal subjected totransmission processing, via antenna 204.

Thus, according to the present embodiment, when the number of RB'sincreases, that is, when the ZC sequence length N is longer, a sequencegroup is generated using sequences that make the difference between r/Nand rb/Nb smaller, and allocated to the single cell. By this means, itis possible to maintain a predetermined number of sequences in each RBwhile reducing cross-correlation between different sequence groups,thereby reducing inter-cell interference.

Also, although an example case has been described above with the presentembodiment where the sequence length of one RB is used as the referencesequence length Nb in ST 101, the present invention is not limited tothis, and it is equally possible to set the reference sequence length Nbadaptively. For example, taking into account that, amongst ZC sequencesforming a certain sequence group, the reference ZC sequence has thelowest cross-correlation with other sequence groups, the referencesequence length Nb is the sequence length associated with the number ofRB's used in a radio mobile station apparatus in the cell edge of thepoorest received quality. By this means, it is further possible toreduce inter-cell interference.

Also, in a cellular communication system, it is equally possible to setthe reference sequence length Nb based on the number of sequence groupsrequired to reduce inter-cell interference. For example, when the numberof sequence groups required is 100, the sequence length that is theclosest to 100, that is, a sequence length of 109, associated with nineRB's, is set as the reference sequence length Nb. It is possible togenerate 108 ZC sequences from nine RB's, that is, from a sequencelength of 109, so that it is possible to select 100 reference sequencenumber r's from 108 reference sequence number r's and generate 100different sequence groups.

Also, an example case has been described above with the presentembodiment where the number of ZC sequences associated with a largernumber of RB's is limited by setting the threshold Xth(m) smaller whenthe number of RB's is larger. However, the present invention is notlimited to this, and it is equally possible to find predetermined ZCsequences arranged in ascending order of the difference between r/N andrb/Nb, and form a sequence group. That is, ZC sequences that make thedifference between r/N and rb/Nb smaller are preferentially selecteduntil the number of ZC sequences reaches a predetermined number. If thesequences are arranged based on the magnitude of r/N, the intervalbetween sequences is 1/N, and the interval between sequences is smallerwhen an RB is larger (i.e. N is larger). Therefore, by the process oflimiting the number of sequences, it is possible to provide the sameeffect as provided in the process of making the threshold Xth (m)smaller when an RB is larger. That is, even if sequence groups aregenerated in the above way, it is equally possible to provide an effectof reducing cross-correlation between sequence groups.

Also, an example case has been described above with the presentembodiment where the reference sequence length Nb signaled from radiobase station apparatus 100 to radio mobile station apparatus 200, withan assumption that the reference sequence length Nb varies betweencells. However, the present invention is not limited to this, and, if areference sequence length Nb that is common between all cells isdetermined in advance, signaling is not necessary. Alternatively, it isequally possible to determine in advance the reference number of RB'sinstead of the reference sequence length Nb. The numbers of RB's andsequence lengths are uniquely associated, so that it is possible toderive the reference sequence length Nb from the reference number ofRB's.

Also, an example case has been described above with the presentembodiment where sequence number calculating section 1002 calculates theusable sequence number r using the reference sequence number rb, thereference sequence length Nb and the number of RB's m. However, thepresent invention is not limited to this, and, if radio base stationapparatus 100 and radio mobile station apparatus 200 hold the sequencegroups shown in FIG. 10A and FIG. 10B or the sequence groups shown inFIG. 12A and FIG. 12B in the form of tables, sequence number calculatingsection 1002 may calculate the usable sequence number r by looking upthese tables. An example method of determining the sequence number rusing these tables will be explained below. For example, with anassumption that the reference sequence length Nb is fixed, tables areprepared for the two parameters of sequence length N and referencesequence number rb, and selectable r's are described therein. In thisexample, radio mobile station apparatus 100 receives the sequence lengthN and reference sequence number rb signaled from radio base stationapparatus 200, refers to the tables associated with these items anddetermines a Zadoff-Chu sequence that should be used as a referencesignal by selecting in a random manner one of the described values thatr might assume.

Also, an example case has been described above with the presentembodiment where parameter determining section 1003 selects one ofusable sequence numbers r's based on the frame number or slot number.However, the present invention is not limited to this, and parameterdetermining section 1003 may select the minimum or maximum sequencenumber from usable sequence number r's.

Embodiment 2

The sequence allocating method according to Embodiment 2 of the presentinvention is based on the cross-correlation characteristic of ZCsequence ascertained by computer simulation by the present inventors.

FIG. 16 is a diagram illustrating the cross-correlation characteristicof ZC sequence ascertained by computer simulation by the presentinventors.

In FIG. 16, the horizontal axis represents the difference of r/N betweenZC sequences of different transmission bandwidths or different sequencelengths, and the vertical axis represents the cross-correlationcharacteristic. As shown in FIG. 16, if the difference of r/N between ZCsequences of different transmission bandwidths or different sequencelengths is 0.0, the cross-correlation between ZC sequences is thelargest, and, if the difference of r/N is 0.5, the cross-correlationbetween ZC sequences forms a peak. That is, the cross-correlationbetween ZC sequences of different transmission bandwidths or differentsequence lengths increases when the difference of r/N is closer to 0.5.

The sequence allocating method according to the present embodiment has afeature of excluding a ZC sequence that makes a difference of r/N fromthe reference ZC sequence close to 0.5, from a sequence group.

FIG. 17 is a flowchart showing the process of the sequence allocatingmethod in a cellular radio communication system according to the presentembodiment. Here, in the process in FIG. 17, the same process as in FIG.8 will be omitted.

In ST 201, as an existing sequence group, a sequence group formed withZC sequences, in which the difference between r/N and rb/Nb is equal toor less than 1/26 regardless of the number of RB's, is inputted.

In ST 202, according to following equation 8, the threshold Xth2(m) isset in a case where the number of RB's is m. That is, Xth2(m) is sethigher by a predetermined value every time the number of RB's increases.Xth2(m)=(m−1)×0.0012  (Equation 8)

In ST 203, whether or not r and N satisfy following equation 9 isdecided.∥r/N−rb/Nb|−0.5|≦Xth2(m)  (Equation 9)

In ST 203, if r and N are decided to satisfy equation 9 (“YES” in ST203), the process of ST 204 is performed.

In ST 204, the ZC sequence having r as a sequence number is deleted fromthe existing sequence group inputted in ST 201

By contrast, if r and N are decided not to satisfy equation 9 (“NO” inST 203), the process of ST 108 is performed.

FIG. 18 is a diagram illustrating a method of generating sequence groupsaccording to the process of the sequence allocating method in FIG. 17.

In FIG. 18, group X represents a sequence group including a referencesequence, and group Y represents an existing sequence group inputted inST 201. Here, the hatched region represents ZC sequences in which thedifference between r/N and rb/Nb in group X is close to 0.5, forexample, in which the r/N difference stays within a range of(0.5−Xth2(m)) to (0.5+Xth2(m)). As shown in FIG. 18, in the sequenceallocating method according to the present embodiment, ZC sequences, inwhich the difference between r/N and rb/Nb in group X stays within therange of (0.5−Xth2(m)) to (0.5+Xth2(m)), are deleted from the existingsequence group Y. By this means, cross-correlation between sequencegroups is reduced. Also, according to equation 8, by setting thethreshold Xth2(m) smaller when the number of RB's decreases and byreducing the number of sequences deleted, the number of ZC sequencesdeleted from a sequence group is limited.

FIG. 19A and FIG. 19B illustrate examples of sequence groups acquired bythe sequence allocating method according to the present embodiment. Tobe more specific, the sequence groups shown in FIG. 19A and FIG. 19B (ZCsequence group 1 and ZC sequence group 8) are acquired according to thefollowing conditions and process. For example, to generate ZC sequencegroup 1 shown in FIG. 19A, in ST 101, the reference sequence length Nbis set to 13, and the reference sequence number rb is set to 1. Here, anexisting sequence group is comprised of sequences in which thedifference from rb/Nb is equal to or less than 1/26, regardless of thenumber of RB's. In ST 202, using equation 8, the threshold Xth2(m)associated with the number of RB's is set, and a ZC sequence thatsatisfies equation 9 in ST 204 is deleted from the existing sequencegroup.

Thus, according to the present embodiment, upon generating sequencegroups, the threshold Xth2(m) is set smaller when the number of RB's issmaller, and a ZC sequence, in which the difference between r/N andrb/Nb stays within a range of (0.5−Xth2(m)) to (0.5+Xth2(m)), is deletedfrom an existing sequence group. By this means, it is possible to reducethe cross-correlation between sequence groups and reduces inter-cellinterference while maintaining the number of sequences forming sequencegroups.

Also, an example case has been described above with the presentembodiment where a sequence group comprised of ZC sequences, in whichthe difference between r/N and rb/Nb is equal to or less than 1/26,regardless of the number of RB's, is inputted as an existing sequencegroup in ST 201. However, the present invention is not limited to this,and it is equally possible to input a sequence group acquired inEmbodiment 1 as an existing sequence group.

Also, although an example case has been described above with the presentembodiment where a ZC sequence, in which the difference between r/N andrb/Nb stays within a range of (0.5−Xth2(m)) to (0.5+Xth2(m)), is deletedfrom an existing sequence group, the present invention is not limited tothis, and, it is equally possible to further add conditions for deletingZC sequences from a sequence group and delete only sequences associatedwith the numbers of RB's equal to or greater than a predetermined value,for example, 10. By this means, it is possible to prevent ZC sequencesassociated with smaller numbers of RB's from being deleted excessivelyand limit the number of ZC sequences deleted.

FIG. 20A and FIG. 20B show examples of sequence groups acquired when thenumber of RB's allowing a sequence to be deleted, is set 10 or more.Here, other conditions for acquiring the sequence groups shown in FIG.20A and FIG. 20B (i.e. ZC sequence group 1 and ZC sequence group 8) arethe same as the conditions for acquiring the sequence groups shown inFIG. 19A and FIG. 19B.

Also, an example case has been described above with the presentembodiment where whether or not r and N satisfy equation 9 is decided inST 203, the present invention is not limited to this, and it is equallypossible to use following equation 10. By this means, it is possible todelete the same sequences as in the case of using equation 9, from asequence group.∥r/N−rb/Nb|−(0.5/Nb)|≦Xth2(m)  (Equation 10)

Also, an example case has been described above with the presentembodiment where one sequence length, that is, one kind of the number ofRB's is used as a reference in equation 9. However, the presentinvention is not limited to this, and it is equally possible to providea plurality of reference sequence lengths used for a decision inequation 9, that is, a plurality of the reference numbers of RB's. Forexample, using three references of Nb₁=13, Nb₂=29 and Nb₃=37 associatedwith one RB, two RB's and three RB's, all sequences in which∥r/N−rb₁/Nb₁|−0.5| is lower than a threshold, ∥r/N−rb₂/Nb₂|−0.5| islower than a threshold and ∥r/N−rb₃/Nb₃|−0.5| is lower than a threshold,are deleted. Here, a plurality of the reference numbers of RB's need notbe consecutive. For example, it is possible to set one RB and three RB's(i.e. N=13 and N=37) as the reference sequence length Nb.

Also, an example case has been described above with the presentembodiment where ZC sequences, in which the difference between r/N andrb/Nb stays within a range of (0.5−Xth2(m)) to (0.54−Xth2(m)), aredeleted from an existing sequence group. However, the present inventionis not limited to this, and it is equally possible to further add theconditions of maintaining (leaving) predetermined sequences based oneach number of RB's. To be more specific, the number of sequences p(m)to be maintained is set in advance in each RB, sequences are deleted inorder from the sequence in which the difference between r/N and rb/Nb isthe closest to 0.5, and deletion processing is stopped when the numberof remaining sequences is p(m). By this means, it is possible tomaintain required sequences in each RB.

Embodiments of the present invention have been explained above.

The sequence allocating method according to the present invention is notlimited to the above embodiments, and can be implemented with variouschanges. For example, the above embodiments can be implemented withadequate combinations.

Also, in the above embodiments, as further conditions for generatingsequence groups, sequences, in which CM (Cubic Metric) or PAPR isgreater than a predetermined value, such as CM or PAPR in QPSK, may notbe used and may be deleted from a sequence group. In this case, themagnitude of CM or PAPR is less biased between sequence groups, so that,even if such conditions are added, it is possible to make the number ofsequences substantially equal between sequence groups, and the number ofsequences that can be used in each sequence group is not biased.

Also, although an example case has been described above with embodimentswhere sequence groups are formed using frequency domain ZC sequences,the present invention is not limited to this, and it is equally possibleto form sequence groups using ZC sequences that are generated in thetime domain. Here, time domain ZC sequences and frequency domain ZCsequences satisfy the relationship represented by following equation 11.(u×r)mod(N)=N−1  (Equation 11)

In equation 11, N represents the ZC sequence length, r represents thesequence number of time domain. ZC sequence, and u represents thesequence number of frequency domain ZC sequence. Therefore, when asequence group is formed using time domain ZC sequences, ZC sequences,in which the difference of u/N from the reference sequence is less thana predetermined threshold, are found. Time domain ZC sequences andfrequency domain ZC sequences share the same characteristics, andtherefore the same effect is acquired.

Also, although an example case has been described above with embodimentswhere a ZC sequence is used as a reference signal for channelestimation, the present invention is not limited to this, and it isequally possible to use a ZC sequence as, for example, a referencesignal for CQI estimation (i.e. sounding RS), synchronization channel,random access preamble signal, CQI signal or ACK/NACK signal.

Also, although an example ease has been described above with embodimentswhere a ZC sequence is used as a reference signal from a radio mobilestation apparatus to a radio base station apparatus, the presentinvention is not limited to this, and it is equally possible to applythe present invention to a case where a ZC sequence is used as areference signal from a radio base station apparatus to a radio mobilestation apparatus.

Also, although an example case has been described above with embodimentswhere a ZC sequence is used as a reference signal, it is equallypossible to use, for example, a GCL (Generalized Chirp-Like) sequencec(k) represented by following equation 12, as a reference signal.c(k)=a(k)b(k mod m),k=0,1, . . . , N−1  (Equation 12)

In equation 12, N represents the sequence length, and the relationshipof N=sm² (where s and m are integers) or N=tm (where t and in areintegers) holds. Here, a(k) is the ZC sequence represented by equation 1or equation 2, and b(k) is a DFT sequence represented by followingequation 13.[3]b _(i)(k)=W _(m) ^(ik) , i,k=0,1, . . . , m−1  (Equation 13)

Also, although the above embodiments use the condition “equal to or lessthan a threshold” as a decision condition, it is equally possible to usethe condition “less than a threshold” as a decision condition.

Also, the above embodiments have been described using Zadoff-Chusequences. However, Zadoff-Chu sequences are not limited to thesequences represented by the above equations, and include a sequencegenerated by repeating part of a Zadoff-Chu sequence, a sequencegenerated by truncating part of a Zadoff-Chu sequence and a sequencegenerated by removing part of a Zadoff-Chu sequence.

Although a case has been described above with embodiments as an examplewhere the present invention is implemented with hardware, the presentinvention can be implemented with software.

Furthermore, each function block employed in the description of each ofthe aforementioned embodiments may typically be implemented as an LSIconstituted by an integrated circuit. These may be individual chips orpartially or totally contained on a single chip. “LSI” is adopted herebut this may also be referred to as “IC,” “system LSI,” “super LSI,” or“ultra LSI” depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be reconfigured is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosure of Japanese Patent Application No. 2007-160348, filed onJun. 18, 2007, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The sequence allocating method, transmitting method and radio mobilestation apparatus according to the present invention can reducecross-correlation between different sequence groups while maintainingthe number of ZC sequences forming a sequence group, and are applicableto a cellular radio communication system.

1. A transmission apparatus comprising: a receiving section configuredto receive control information related to transmission bandwidth of areference signal; a generating section configured to generate thereference signal using one of sequence(s) which are grouped into agroup, wherein Nb is a reference sequence length which is common to allcells, and a predefined number of the sequence(s) with sequencenumber(s) r in ascending order of absolute value of difference betweenrb/Nb and r/N are grouped into the group with a group number rb for asequence length N which depends on the transmission bandwidth based onthe control information; and a transmitting section configured totransmit the reference signal.
 2. The transmission apparatus accordingto claim 1, wherein the sequence is a Zadoff-Chu sequence ar(k) definedby${a_{r}(k)} = {\mathbb{e}}^{{- j}\frac{2\pi\; r}{N}{({{{k{({k + 1})}}/2} + {qk}})}}$wherein k and q are arbitrary integers.
 3. The transmission apparatusaccording to claim 1, wherein the sequence length N corresponds to thetransmission bandwidth uniquely.
 4. The transmission apparatus accordingto claim 1, wherein said generating section groups sequence(s) withsequence number(s) r by which the absolute value for the sequence lengthN is smalleras the transmission bandwidth is wider.
 5. The transmissionapparatus according to claim 1, wherein said generating section limits anumber of the sequence(s) available for the sequence length N bygrouping the predefined number of the sequence(s).
 6. The transmissionapparatus according to claim 1 further comprising a receiving sectionconfigured to receive control information related to the group numberrb, wherein said generating section generates the reference signal usingone of the grouped sequence(s) based on the control information.
 7. Thetransmission apparatus according to claim 1, wherein said generatingsection generates the reference signal using one of the groupedsequence(s) according to a cell.
 8. The transmission apparatus accordingto claim 1, wherein the reference signal is a sounding reference signal(sounding RS).
 9. The transmission apparatus according to claim 1,wherein said generating section generates the reference signal using onesequence which is selected among the grouped sequence(s) with sequencehopping.
 10. The transmission apparatus according to claim 1, whereinsaid generating section generates the reference signal using onesequence which is selected among the grouped sequence(s) with sequencehopping based on a frame number or slot number.
 11. A transmissionapparatus comprising: a receiving section configured to receive controlinformation related to transmission bandwidth of a reference signal; agenerating section configured to generate the reference signal using oneof sequence(s) which are grouped into a group, wherein Nb is a referencesequence length which is common to all cells, and the sequence(s) withsequence number(s) r, by which absolute value of difference betweenrb/Nb and r/N is less than or equal to a predetermined value, aregrouped into the group with a group number rb for a sequence length Nwhich depends on the transmission bandwidth based on the controlinformation; and a transmitting section configured to transmit thereference signal, wherein the predetermined value for the widetransmission bandwidth is smaller than that for the narrow transmissionbandwidth.
 12. The transmission apparatus according to claim 11, whereinthe wider the transmission bandwidth is, the smaller the predeterminedvalue is.
 13. The transmission apparatus according to claim 11, whereina definition of the predetermined value is different across a thresholdvalue.
 14. A method for generating reference signal comprising:receiving, at a transmission apparatus, control information related totransmission bandwidth of a reference signal; and generating thereference signal using one of sequence(s) which are grouped into agroup, wherein Nb is a reference sequence length which is common to allcells, and a predefined number of the sequence(s) with sequencenumber(s) r in ascending order of absolute value of difference betweenrb/Nb and r/N are grouped into the group with a group number rb for asequence length N which depends on the transmission bandwidth based onthe control information.
 15. The method for generating reference signalaccording to claim 14, wherein the sequence is a Zadoff-Chu sequencear(k) defined by${a_{r}(k)} = {\mathbb{e}}^{{- j}\frac{2\pi\; r}{N}{({{{k{({k + 1})}}/2} + {qk}})}}$wherein k and q are arbitrary integers.
 16. The method for generatingreference signal according to claim 14, wherein the sequence length Ncorresponds to the transmission bandwidth uniquely.
 17. The method forgenerating reference signal according to claim 14, wherein saidgenerating section groups sequence(s) with sequence number(s) r by whichthe absolute value for the sequence length N is smalleras thetransmission bandwidth is wider.
 18. The method for generating referencesignal according to claim 14, wherein a number of the sequence(s)available for the sequence length N is limited by grouping thepredefined number of the sequence(s).
 19. The method for generatingreference signal according to claim 14 further comprising: receivingcontrol information related to the group number rb, wherein thereference signal is generated using one of the grouped sequence(s) basedon the control information.
 20. The method for generating referencesignal according to claim 14, wherein the reference signal is generatedusing one of the grouped sequence(s) according to a cell.
 21. The methodfor generating reference signal according to claim 14, wherein thereference signal is a sounding reference signal (sounding RS).
 22. Themethod for generating reference signal according to claim 14, whereinthe reference signal is generated using one sequence which is selectedamong the grouped sequence(s) with sequence hopping.
 23. The method forgenerating reference signal according to claim 14, wherein the referencesignal is generated using one sequence which is selected among thegrouped sequence(s) with sequence hopping based on a frame number orslot number.
 24. A method for generating reference signal comprising:receiving, at a transmission apparatus, control information related totransmission bandwidth of a reference signal; and generating thereference signal using one of sequence(s) which are grouped into agroup, wherein Nb is a reference sequence length which is common to allcells, and the sequence(s) with sequence number(s) r, by which absolutevalue of difference between rb/Nb and r/N is less than or equal to apredetermined value, are grouped into the group with a group number rbfor a sequence length N which depends on the transmission bandwidthbased on the control information, wherein the predetermined value forthe wide transmission bandwidth is smaller than that for the narrowtransmission bandwidth.
 25. The method for generating reference signalaccording to claim 24, wherein the wider the transmission bandwidth is,the smaller the predetermined value is.
 26. The method for generatingreference signal according to claim 24, wherein a definition of thepredetermined value is different across a threshold value.